Multisite cardiac pacemakers are known. EP-A-0 030 897 describes such multisite pacemakers, in which there are two outputs and the corresponding stimulation electrodes are implanted in two predetermined sites belonging to the same cardiac cavity, notably the ventricle. A switching device allows one to choose the functioning mode of the pacemaker among various modes (bipolar, double unipolar, double unipolar or bifocal ventricular), nevertheless without modifying the implantation of electrodes and the choice of stimulation sites.